So I'm asking for advice, I've tried everything, its a 1991 RS with a 350 carb swap. Brandspankingnew Afco Racing radiator, new Edelbrock hi-flow pump, tried with 195 thermostat, cut open thermostat, no thermostat, and now 180, tried the "water wetter" stuff, tried two 16" fans (one pulling one pushing), one racing 16" fan, and currently, three 10" fans. I've done a hydrocarbon/vacuum test, and no hydrocarbons, and it held vacuum while running. Now since there is no hydrocarbons and it holds vacuum, seems to put headgasket out of the equation, I was pondering maybe it has a cracked cylinder wall perfectly between two, or maybe it possibly has a cracked head perfectly on the top of the compression chamber, those are the only ideas left, please, if anyone has ANY thoughts, advise. If it turns out to be this engine, I have another one out of my '77 Chevy 4X4 to throw in it, just afraid to destroy my trans, rear end, and twist my car (2002 vortec, 383, cam, pistons, fastburn vortec heads, 455hp, 555ft/lbs, powerban 4-7 thousand rpms) so, im in a conundrum and stuck.

 

Is the new water pump CW or CCW rotation?

 

hows the car running is it lean because that will cause it to run hot have you replaced the therostat maybe its off givving you a higher reading definatly check the rotation of the water pump and the little air scoop so famous on the thirdgens not only scoops the air but keeps the fans from pulling hot air from the engine bay.

If you fuel pressure is low and or bad ajustments on the carb can cause a lean condition

 

Radiator cap holding pressure?
Lower radiator hose soft & collapse?

( edit )
Air dam & duct in place?

 

Waterpump is reverse rotation (it still has serpentine system), is not running lean, had three different carbs on it, all tuned more rich than lean, air dam is in place, even metal strapped it so it cannot bend backwards (it had small cracks running up the sides) and my overheating happens if im below 25 or above 55, so air dam/ducts wouldn't be problem (doesn't do anything until highway speeds), checked my gauge multiple ways, it is dead-on. basically it will go up to 180 and back down a few about six times (thermo opening and closing) then it will get up to 210 and sit there for quite awhile, it will slowly rise, and then jump to 230, i never let it get any hotter than that since it is the old style block, it seems to do it whenever there is load on the engine, because once it gets to 230 on the highway i can get it up and push the clutch in and coast it will cool down at least five degrees, and if you turn the A/C on it overheats immediately

 

when i was driving from CT to FL my alt caused the car to over heat basically it was working fine volts ect but the amps were to low and when the fans kicked on they were not full speed and sitting in traffic was ok but at highway speeds it was up at 230 240 I just drove till I hit FL then soon after the car got a new engine with a LT1 swap

 

Could be in your a'c compressor. Go at a slow speed and note if your engine surges as the compressor kicks in and out. If it does it can be dragging the system and causes the overheating.

 

I just fixed my over heating problem, got a Airdam deflector and works great! Hasn't over heated sense. I did everything prior to replacing it, many guys on here told me to get one. I just kept replacing parts thinking I could figure it out. Well the Airdam worked great!

 

Did you replace the Stock one?? What's the Diff, I'm in Southern Az as well and my overheating is occurring at freeway speeds??? I'm running a 160 Thermos, new Rad, and flushed???

 

Not air dam, mine is in place and correct, not A/C because it doesnt matter if A/C is on or off, on it just overheats quicker. If I can't come up with an answer by Tues. I'm swapping my H/O into it. Only going to be about $90 unless my flywheel is wrong (I'm hoping its OE because then itll match with my one piece, if its two piece I'm gonna have to find one somewhere)

 

This happens only at highways speeds and not in town? If it happens only at highway speeds, it's not your fans. Have you replaced all of your hoses? If they are older, they can get soft and "squeeze" themselves shut from the pressure of the water running through them restricting the flow. It "could" be crud in the block, or there could be an obstruction to the radiator, i.e. if you got a bunch of junk between the condenser and the radiator, that may cause an issue, but I'd start with the hoses.

 

Like I said before, it happens both at highway and in town. doesnt matter. if there is load on the engine, it overheats. nothing in the condenser or or radiator or in between, the hoses do not collapse.

 

Hmm, running lean will cause it to run hot. Have you burped the system to make sure there is no trapped air pockets? Run it with the radiator cap off till the car warms up to running temp. The radiator will bubble over when it hits an air pocket and then the fluid level will drop noticably. I had to do this when I put my new motor in. Make sure you have the heater turned on as well to get coolant to flow through the heater core.

 

hows your catalytic converter?

 

Are you sure it actually overheats, or are you just going by the dash gauge? You haven't mentioned having any symptoms. Got rough running, loss of power, boiling the expansion tank etc?

The stock gauges/senders can be inaccurate, by many accounts. Can you shoot around with a laser temp gun to verify the gauge?

 

It has no heater (bypassed the core) not running lean, I used a burping tool (special gravity feed jug attached to special radiator cap) it burped until the thermostat opened 8 times, have aftermarket temp and oil pressure gauges, I have checked with a laser temp, its dead on. the second it hits 230 it has almost no power, it drops cylinder #8, and im going to knock the Cat out. I am proceeding with the engine swap. already most of the way done prep wise (accessories off, wiring out of way, rad out)

 

Do you think the intake gaskets are on backwards?

 

If you're pulling it too late now, but 2 more thoughts - ignition timing not to the motor's liking, and do you have duct(s) fully surrounding whatever fan setup you ended up with, so hot air can't recirculate back thru the fan(s).

Sounds like you've really gone the extra mile to solve this, pls post back once it's swapped and let us know what it was!

 

Water flows great from thermostat housing out water pump flanges, so i dont believe gaskets are backwards. I have it timed like all of my vehicles, 8 degrees BTDC @ 500rpm. Runs great like that when it wants. this is my fan setup.

 

using the same temperature gauge maybe she really isnt overheating?

 

Well, my gauge reads 20* hotter than it really is, so my only advice now, sinc we've seemed to try everything that I know to look for, is that if it's not boiling over into the catch can, it's not overheating...

 

Doesn't look like nearly enough fan, there's large areas of the core still exposed. I chased terrible overheating issues the first couple of years I owned my car. Like you, I tried all sorts of fans combos - the original factory single, a new larger single, a couple of pushers in front, all 3 at once. Nothing made a difference.

The ultimate fix was in the shrouding. I went to the wreckers, and found the largest fans I could find that would completely fill the rad core. 2 fully shrouded rear-mounted fans, where the shrouds cover close to 100% of the rad core.

This forces air to be pulled from across the whole core, rather than leaving dead spots like you have. It also stops the fans sucking air in from the sides, instead of pulling it thru the core.

Edit: That also looks like quite a small radiator - does it fill the whole width of the rad support, or is it really larger than it looks in the pic?

 

I had temp spikes on a 5.7, turned out to be head gaskets. I have a 91 RS with stock 305 and I'm having overheating issues, just going through the threads soaking up the knowledge.

 

i had new lower rad hose colapse when ran above idle when hot caused overheat went to universal with spring cured problem